Simplify the following expression: $k = \dfrac{5}{2a} - \dfrac{1}{4a}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $2a$ and $4a$ $\lcm(2a, 4a) = 4a$ $ k = \dfrac{2}{2} \cdot \dfrac{5}{2a} - \dfrac{1}{1} \cdot \dfrac{1}{4a} $ $k = \dfrac{10}{4a} - \dfrac{1}{4a}$ $k = \dfrac{10 -1}{4a}$ $k = \dfrac{9}{4a}$